The present invention relates to the general field of turboprops having at least one set of fan blades of adjustable pitch. The invention relates more particularly to controlling the pitch of the fan blades of an airplane turboprop having two propellers.
In known manner, a two-propeller airplane turboprop comprises a turbine driving two contrarotating rotors, each driving a set of unducted fan blades. By way of example, reference may be made to document GB 2 129 502, which describes various ways of embodying such a turboprop.
In that type of turboprop, the pitch of the fan blades in each set (i.e. the angular orientation of each blade about a radial axis) constitutes one of the parameters making it possible to control the thrust from the turboprop and the speed of rotation of the propellers.
Various solutions have been proposed for controlling the pitch of the fan blades in a given set. By way of example, reference may be made to patent applications FR 2 946 010, FR 2 946 011, and FR 2 946 012 filed by the Applicant. In those documents, in order to adjust the pitch of the blades, provision is made to couple them to a synchronizing ring that can be turned by means of a central actuator and a connecting arm.